Revision as of 11:41, 14 September 2017

Summary

The Refine SOP allows you to increase the number of CVs in any NURBS, Bzier, or polygonal surface or face without changing its shape. It is also used to decrease the number of CVs within a given tolerance (i.e. a simple but fast method of data reduction).

The Difference Between Refinement and Unrefinement

Refinement and unrefinement work both on faces (polygons, Bzier curves and NURBS curves) and surfaces (primitive meshes, Bzier surfaces and NURBS surfaces). To unrefine a face or a surface you need to specify a parametric interval (not just a single value as in refinement). This allows you to unrefine primitives within arbitrary intervals, either locally or globally. For example, to unrefine the whole primitive choose 0 and 1 as the two parametric boundaries; [0,0.5] will unrefine only the first parametric half of the primitive.

The interval boundaries are given by the First/Second U/V fields. Since refinement does not need an interval, the Second U/V fields are disabled by default.

The Tolerance control is only available for unrefinement, and not for refinement. Refinement does not need tolerances because it generates a curve or a surface that is mathematically identical to the original. Unrefinement, however, may tend to smooth out (or "melt") the original in a given area. In short, unrefinement is lossy; refinement isn't.